Image decoding method, image coding method, image decoding apparatus, image coding apparatus and integrated circuit for generating a code stream with a hierarchical code structure

ABSTRACT

An image decoding method decodes a coded stream which includes plural processing units and a header of the processing units, and which is generated by coding a moving picture using inter prediction, the processing units including at least one processing unit divided in a hierarchy, the hierarchy including: a highest hierarchical layer in which a coding unit exists as a largest processing unit; and a lower hierarchical layer in which a prediction unit exists. The method comprises: identifying, by parsing hierarchy depth information stored in the header and indicating a hierarchical layer higher than a lowest hierarchical layer in which a smallest prediction unit exits, a hierarchical layer which is indicated by the hierarchy depth information or a hierarchical layer higher than the indicated hierarchical layer, the hierarchical layer having a prediction unit in which a reference index is stored; and decoding the prediction unit, using the reference index.

TECHNICAL FIELD

The present invention relates to an image coding method for codingimages or moving pictures included in multimedia data and an imagedecoding method for decoding coded images or moving pictures.

BACKGROUND ART

In video compressions standards like MPEG-1, MPEG-2, MPEG-4, or MPEG-4AVC, a compressed picture is usually divided into rectangular unitscalled “macroblocks”. A macroblock is usually defined as atwo-dimensional block of image samples. The image samples have a widthof 16 pixels and a height of 16 pixels for luminance samples. Thecompression ratio for the macroblock is controlled by a quantizationscale parameter for each macroblock. The quantization scale parameterdetermines the level of quantization to be applied to all the frequencycoefficients. The quantization scale parameter is usually coded as adifference value from the quantization scale parameter of the previousmacroblock in cording order, and is stored in a compressed macroblockheader.

In new video standards under development, for example, the HighEfficiency Video Coding (HEVC) standard by the MPEG standardizationbodies, it is suggested that dividing the picture into large units canimprove the coding efficiency of the compressed video (for example,refer to Non Patent Literature 1). In other words, a picture can bedivided into coding units (CU) where each coding unit has a size thatcan be much larger than a macroblock. For example, the coding unit sizecan be 128 pixels by 128 pixels for luminance samples, which isapproximately 64 times larger than a macroblock.

A large coding unit can be sub-divided into smaller units (sub codingunits) to achieve better coding efficiency. Each coding unit or subcoding unit has three main components. The main components are a codingunit header, a prediction unit (PU), and a transform unit (TU).

FIG. 1 is a diagram showing the structure of compressed picture havingcoding units.

As shown in FIG. 1, a picture D100 includes a header (hereinafterreferred to as picture header) and a body. The picture header includesparameters related to the picture (picture parameters) while the bodyincludes compressed samples of a picture. Moreover, the body includescoding units such as coding units D102 and D104, and some of the codingunits are divided into sub coding units. For example, the coding unitD102 is divided into sub coding units D106, and one of the sub codingunits 106 is further divided into smaller sub coding units D108. Thecoding unit D104 or sub coding unit D108 has three main components. Morespecifically, the coding unit D104 includes a coding unit header D116, aprediction unit D118, and a transform unit D120 as the three maincomponents. The sub coding unit D108 has a sub coding unit header D110,a prediction unit D112, and a transform unit D114 as the three maincomponents. As shown in FIG. 1, a transform unit D120 is divided intosmall sub transform units D122, and one of the sub transform units D122is divided into smaller sub transform units D124. The smallest transformunits (sub transform units) D114 and D124 includes the quantizedcoefficients of a block, which requires a quantization scale parameterfor the inverse quantization process of the coefficients.

CITATION LIST Non Patent Literature

[NPL 1]

[Non Patent Literature]

“Test Model under Consideration” Joint Collaborative Team on VideoCoding (JCT-VC) of ITU-T SG16 WP3 and ISO/IEC JTC1/SC29/WG11, 2ndMeeting: Geneva, CH, 21-28 Jul., 2010, Document: JCTVC-B205

SUMMARY OF INVENTION Technical Problem

However, in the image decoding method and the image coding methodaccording to the above described Non Patent Literature 1, there is aproblem that coding efficiency cannot be increased.

In other words, in the HEVC standard, the prediction of a coding unit isperformed using at least one prediction unit. The CU on which interprediction is performed is divided into four PUs. The division of the PUmay be performed symmetrically or asymmetrically. The smallest size ofthe PU on which inter prediction is performed is a 4×4 luminance sample.A reference index (ref_idx) is transmitted on a per PU basis. It shouldbe noted that the reference index is also called a reference frameindex, and is an index indicating a reference image which is referred inthe inter prediction. Here, the same reference index tends to be usedfor a small PU including the 4×4 sample and the like. Therefore, thetransmission of the reference index for each of the small PUs makes acoded stream redundant, and consumes unnecessary bits. In other words,since an image coding apparatus needs to always transmit the referenceindex for each of the PUs, an overhead is increased when the referenceindex does not have to be switched in a small region such as a small PU.As a result, coding efficiency cannot be increased.

Therefore, the present invention is conceived in view of the problem,and an object of the present invention is to provide an image decodingmethod and an image coding method for improving coding efficiency.

Solution to Problem

In order to achieve the above described goal, an image decoding methodaccording to an aspect of the present invention is an image decodingmethod for decoding a coded stream which includes a plurality ofprocessing units and a header of the processing units, the coded streambeing generated by coding a moving picture using inter prediction, theprocessing units including at least one processing unit divided into aplurality of sub processing units in a hierarchy which decrease in sizefrom a higher level to a lower level, the hierarchy including: a highesthierarchical layer in which a coding unit exists as a largest processingunit; and a lower hierarchical layer which is deeper than the highesthierarchical layer and in which a prediction unit exists as a processingunit smaller than the coding unit, the image decoding method comprising:identifying, by parsing hierarchy depth information stored in the headerand indicating a hierarchical layer higher than a lowest hierarchicallayer in which a smallest prediction unit exits, a hierarchical layerwhich is indicated by the hierarchy depth information or a hierarchicallayer higher than the indicated hierarchical layer, the hierarchicallayer having a prediction unit in which a reference index necessary fordecoding is stored; and decoding the prediction unit, using thereference index stored in the prediction unit at the identifiedhierarchical layer.

With this, since the prediction unit in which the reference index isstored is located at a higher hierarchical layer than the lowesthierarchical layer, the prediction unit includes a plurality of smallerprediction units. Since the prediction unit is decoded using thereference index stored in the prediction unit, the same reference indexis used for each of the smaller prediction units included in theprediction unit. Therefore, the image coding apparatus does not have torepeatedly transmit the same reference index by repeatedly inserting thereference index into the small prediction units. As a result, codingefficiency can be increased.

In other words, in the image decoding method according to an aspect ofthe present invention, the smallest unit (smallest transmission unit) isintroduced for transmitting the reference index such as a coding unitincluding an 8×8 sample in order to solve the above described problem.The smallest transmission unit is indicated by, for example, CUhierarchy depth information within a sequence parameter set, a pictureparameter set, or a slice header. A reference index for the smallesttransmission unit is transmitted, and the same reference index is usedfor all the PUs included in the smallest transmission unit.

In other words, the image coding apparatus stores the reference index ina larger unit (processing unit) located at a higher hierarchical layerthan the PU, and stores hierarchy depth information for identifying thehierarchical layer (depth of hierarchical layer) in which the processingunit exists, in a header such as a sequence header or a picture header.The image decoding apparatus identifies the hierarchical layer (depth ofhierarchical layer) by parsing hierarchy depth information located inthe header, and parses the reference index stored in the processing unitlocated in the identified hierarchical layer. The reference index isapplied to all the PUs included in the processing unit. Here, thehierarchy depth information may indicate the deepest (lowest)hierarchical layer in which the processing unit storing the referenceindex can exist. In this case, the image decoding apparatus identifiesthe lowest hierarchical layer indicated by the hierarchy depthinformation or a hierarchical layer that is higher than the lowesthierarchical layer. The hierarchy depth information may be a flag whichindicates whether or not the reference index is stored in the CU at thepredetermined hierarchical layer (for example, the CU located at thelowest layer).

Moreover, in order to achieve the above described goal, an image codingmethod according to an aspect of the present invention is an imagecoding method for generating a coded stream which includes a pluralityof processing units and a header of the processing units, by coding amoving picture using inter prediction, the processing units including atleast one processing unit divided into a plurality of sub processingunits in a hierarchy which decrease in size from a higher level to alower level, the hierarchy including: a highest hierarchical layer inwhich a coding unit exists as a largest processing unit; and a lowerhierarchical layer which is deeper than the highest hierarchical layerand in which a prediction unit exists as a processing unit smaller thanthe coding unit, the image coding method comprising: coding the movingpicture using inter prediction; writing, into the header, hierarchydepth information which is information for identifying a hierarchicallayer having a prediction unit in which a reference index necessary fordecoding is stored and indicates a hierarchical layer higher than alowest hierarchical layer in which a smallest prediction unit exists;and writing, into a prediction unit located at a hierarchical layerindicated by the hierarchy depth information or located higher than theindicated hierarchical layer, the reference index to be applied to theprediction unit.

With this, without repeatedly writing the same reference index into eachof a plurality of small predicting units, only one reference index iswritten into a large processing unit which is located at a higherhierarchical layer than the prediction units and includes the predictionunits. Therefore, the redundancy of the reference index can be removedand coding efficiency can be increased.

It should be noted that the present invention can be implemented as theabove described image decoding method and image coding method. It canalso be implemented as an apparatus for coding or decoding an image, anintegrated circuit, a program for decoding or coding an image accordingto the methods, and a recording medium having the program storedthereon.

Advantageous Effects of Invention

With the image decoding method and the image coding method according tothe present invention, coding efficiency can be increased. Morespecifically, by removing the redundancy in which the reference index iscoded for each of the small PUs, coding efficiency can be increased andthe amount of coding can be reduced.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram showing the configuration of a conventional codedstream.

FIG. 2 is a block diagram showing the configuration of an image codingapparatus according to Embodiment 1 of the present invention.

FIG. 3 is a block diagram showing the configuration of an image decodingapparatus according to Embodiment 1 of the present invention.

FIG. 4 is an illustration diagram for describing a multi-hierarchicalblock structure.

FIG. 5 is a diagram showing a configuration a coded stream beingconsidered under HEVC standard.

FIG. 6 is a diagram showing the configuration of a coded streamaccording to Embodiment 1 of the present invention.

FIG. 7A is a diagram showing a storage position of hierarchy depthinformation (maximum hierarchy depth) according to Embodiment 1 of thepresent invention.

FIG. 7B is a diagram showing a storage position of hierarchy depthinformation (maximum hierarchy depth) according to Embodiment 1 of thepresent invention.

FIG. 8 is a flowchart showing decoding by an image decoding apparatusaccording to Embodiment 1 of the present invention.

FIG. 9 is a flowchart showing coding by an image coding apparatusaccording to Embodiment 1 of the present invention.

FIG. 10 is a flowchart showing decoding by an image decoding apparatusaccording to Variation 1 of Embodiment 1 of the present invention.

FIG. 11 is a flowchart showing decoding of PU by an image decodingapparatus according to Variation 2 of Embodiment 1 of the presentinvention.

FIG. 12A is a flowchart showing the image decoding method according tothe present invention.

FIG. 12B is a flowchart showing the image coding method according to thepresent invention.

FIG. 13A is a diagram showing a syntax of sequence header according toEmbodiment 1 of the present invention.

FIG. 13B is a diagram showing a syntax of picture header according toEmbodiment 1 of the present invention.

FIG. 13C is a diagram showing a syntax of slice header according toEmbodiment 1 of the present invention.

FIG. 14A is a diagram showing a syntax of coding unit (CU) according toEmbodiment 1 of the present invention.

FIG. 14B is a diagram showing a syntax of prediction unit (PU) accordingto Embodiment 1 of the present invention.

FIG. 14C is a diagram showing a syntax of prediction unit (PU) accordingto Embodiment 1 of the present invention.

FIG. 14D is a diagram showing a syntax of transform unit (TU) accordingto Embodiment 1 of the present invention.

FIG. 15 is an overall configuration of a content providing system forimplementing content distribution services.

FIG. 16 shows an overall configuration of a digital broadcasting system.

FIG. 17 shows a block diagram illustrating an example of a configurationof a television.

FIG. 18 shows a block diagram illustrating an example of a configurationof an information reproducing/recording unit that reads and writesinformation from and on a recording medium that is an optical disk.

FIG. 19 shows an example of a configuration of a recording medium thatis an optical disk.

FIG. 20A shows an example of a cellular phone.

FIG. 20B shows a block diagram showing an example of a configuration ofa cellular phone.

FIG. 21 illustrates a structure of multiplexed data.

FIG. 22 schematically shows how each stream is multiplexed inmultiplexed data.

FIG. 23 shows how a video stream is stored in a stream of PES packets inmore detail.

FIG. 24 shows a structure of TS packets and source packets in themultiplexed data.

FIG. 25 shows a data structure of a PMT.

FIG. 26 shows an internal structure of multiplexed data information.

FIG. 27 shows an internal structure of stream attribute information.

FIG. 28 shows steps for identifying video data.

FIG. 29 shows an example of a configuration of an integrated circuit forimplementing the moving picture coding method and the moving picturedecoding method according to each of embodiments.

FIG. 30 shows a configuration for switching between driving frequencies.

FIG. 31 shows steps for identifying video data and switching betweendriving frequencies.

FIG. 32 shows an example of a look-up table in which video datastandards are associated with driving frequencies.

FIG. 33A is a diagram showing an example of a configuration for sharinga module of a signal processing unit.

FIG. 33B is a diagram showing another example of a configuration forsharing a module of the signal processing unit.

DESCRIPTION OF EMBODIMENTS

Hereafter, the embodiments of the present invention will be describedwith reference to the drawings.

[Embodiment 1]

FIG. 2 is a block diagram showing the configuration of an image codingapparatus according to the present embodiment.

An image coding apparatus 1000 includes a coding processing unit 1100and a coding control unit 1200.

The coding processing unit 1100 generates a coded stream by coding amoving picture on a block-by-block basis. The coding processing unit1100 includes a subtractor 1101, an orthogonal transform unit 1102, aquantization unit 1103, an entropy coding unit 1104, an inversequantization unit 1105, an inverse orthogonal transform unit 1106, anadder 1107, a deblocking filter 1108, a memory 1109, an intra predictionunit 1110, a motion compensation unit 1111, a motion estimation unit1112, and a switch 1113.

The subtractor 1101 obtains a moving picture and a prediction image fromthe switch 1113. The subtractor 1101 subtracts the prediction image fromthe current block to be coded included in the moving picture, togenerate a difference image.

The orthogonal transform unit 1102 performs orthogonal transform such asdiscrete cosine transform on the difference image generated by thesubtractor 1101, to transform the difference image into a coefficientblock comprising a plurality of frequency coefficients. The quantizationunit 1103 quantizes each of the frequency coefficients included in thecoefficient block, to generate quantized coefficient block.

The entropy coding unit 1104 generates a coded stream by performingentropy coding (variable length coding) on the coefficient blockquantized by the quantization unit 1103 and a motion vector estimated bythe motion estimation unit 1112.

The inverse quantization unit 1105 performs inverse quantization on thecoefficient block quantized by the quantization unit 1103. The inverseorthogonal transform unit 1106 generates a decoded difference image byperforming inverse orthogonal transform such as inverse discrete cosinetransform on each of the frequency coefficients included in theinversely quantized coefficient block.

The adder 1107 generates a locally decoded image by obtaining aprediction image from the switch 1113 and by adding the prediction imageand the decoded difference image which is generated by the inverseorthogonal transform unit 1106.

The deblocking filter 1108 removes block distortion of the locallydecoded image generated by the adder 1107 and stores the locally decodedimage in the memory 1109.

The intra prediction unit 1110 generates a prediction image byperforming intra prediction on the current block to be coded using thelocally decoded image generated by the adder 1107.

The motion estimation unit 1112 estimates a motion vector for thecurrent block to be coded included in the moving picture, and outputsthe estimated motion vector to the motion compensation unit 1111 and theentropy coding unit 1104.

The motion compensation unit 1111 performs motion compensation on thecurrent block to be coded by referring to the image stored in the memory1109 as a reference image and by using the motion vector estimated bythe motion estimation unit 1112. The motion compensation unit 1111generates, by the motion compensation, a prediction image with respectto the current block to be coded.

When intra predictive coding is performed on the current block to becoded, the switch 1113 outputs the prediction image generated by theintra prediction unit 1110 to the subtractor 1101 and the adder 1107.When inter predictive coding is performed on the current block to becoded, the switch 1113 outputs the prediction image generated by themotion compensation unit 1111 to the subtractor 1101 and the adder 1107.

The coding control unit 1200 controls the coding processing unit 1100.More specifically, the coding control unit 1200 determines a processingunit in which a reference index is stored and hierarchy depthinformation for identifying the location of the processing unit. Thereference index is an index used for inter prediction (motion estimationand motion compensation) by the motion compensation unit 1111 and themotion estimation unit 1112. The processing units according to thepresent embodiment are layered, and one of the processing units at anyhierarchical layer corresponds to the above described block. Thehierarchy depth information, for example, is a parameter for identifyingthe hierarchical layer having a processing unit in which a referenceindex is stored. The coding control unit 1200 instructs the entropycoding unit 1104 to store a reference index in the above determinedprocessing unit and to store the hierarchy depth information in theheader of the coded stream (for example, sequence header or pictureheader).

FIG. 3 is a block diagram showing a configuration of an image decodingapparatus according to the present embodiment.

An image decoding apparatus 2000 includes a decoding processing unit2100 and a decoding control unit 2200.

The decoding processing unit 2100 generates a decoded image by decodinga coded stream on a block-by-block basis. The decoding processing unit2100 includes an entropy decoding unit 2101, an inverse quantizationunit 2102, an inverse orthogonal transform unit 2103, an adder 2104, adeblocking filter 2105, a memory 2106, an intra prediction unit 2107, amotion compensation unit 2108, and a switch 2109.

The entropy decoding unit 2101 obtains a coded stream and performsentropy decoding (variable length decoding) on the coded stream.

The inverse quantization unit 2102 performs inverse quantization on thequantized coefficient block generated by entropy decoding by the entropydecoding unit 2101. The inverse orthogonal transform unit 2103 generatesa decoded difference image by performing inverse orthogonal transformsuch as inverse discrete cosine transform on each of the frequencycoefficients included in the inversely quantized coefficient block.

The adder 2104 generates a decoded image by obtaining a prediction imagefrom the switch 2109 and by adding the prediction image and the decodeddifference image which is generated by the inverse orthogonal transformunit 2103.

The deblocking filter 2105 removes block distortion of the decoded imagegenerated by the adder 2104, stores the decoded image in the memory2106, and outputs the decoded image.

The intra prediction unit 1110 generates a prediction image byperforming intra prediction on the current block to be decoded using thedecoded image generated by the adder 2104.

The motion compensation unit 2108 performs motion compensation on thecurrent block to be decoded by referring to the image stored in thememory 2106 as a reference image and by using the motion vectorgenerated by entropy decoding by the entropy decoding unit 2101. Themotion compensation unit 2108 generates, by the motion compensation, aprediction image with respect to the current block to be decoded.

When intra predictive coding is performed on the current block to bedecoded, the switch 2109 outputs the prediction image generated by theintra prediction unit 2107 to the adder 2104. When inter predictivecoding is performed on the current block to be decoded, the switch 2109outputs the prediction image generated by the motion compensation unit2108 to the adder 2104.

The decoding control unit 2200 controls the decoding processing unit2100. More specifically, the decoding control unit 2200 parses thehierarchy depth information stored in the header of the coded stream(for example, sequence header or picture header), based on the result ofthe entropy decoding by the entropy decoding unit 2101. The decodingcontrol unit 2200 identifies, based on the hierarchy depth information,the hierarchical layer having a processing unit in which a referenceindex is stored and parses the reference index included in theprocessing unit in the hierarchical layer. The decoding control unit2200 instructs the motion compensation unit 2108 to perform interprediction (motion compensation) using the parsed reference index.

FIG. 4 is an illustration diagram for describing a layered processingunit (multi-hierarchical block structure).

The coding processing unit 1100 performs coding on the moving picturefor each of the processing units, and the decoding processing unit 2100decodes the coded stream for each of the processing units. Theprocessing unit is divided into small processing units, and theprocessing unites are layered such that each of the processing units isdivided into smaller processing units. It should be noted that when theprocessing unit is smaller, the hierarchical layer in which theprocessing unit exists is deeper and lower and the value showing thehierarchical layer is greater. In contrast, when the processing unit isgreater, the hierarchical layer in which the processing unit exists isshallow and is in high order and the value showing the hierarchicallayer is small.

The processing unit includes a coding unit (CU), a prediction unit (PU),and a transform unit (TU). CU is a block of maximum 128×128 pixels, andis a unit which corresponds to the conventional macroblock. PU is abasic unit for inter prediction. TU is a basic unit for orthogonaltransform, and the size of TU is the same as the size of the PU or issmaller than the size of the PU by one hierarchical layer. CU is, forexample, divided into four sub CUs, and one of the sub CUs includes thePU and the TU of the same size as the sub CU (in this case, PU and TUare overlapping with each other). For example, the PU is further dividedinto four sub PUs, and TU is also further divided into four sub TUs. Itshould be noted that when the processing unit is divided into smallprocessing units, the small processing unit is referred to as asub-processing unit. For example, when the processing unit is CU, thesub-processing unit is a sub CU. When the processing unit is PU, thesub-processing unit is a sub PU. When the processing unit is TU, thesub-processing unit is a sub TU.

The detail is as follows.

Pictures are divided into slices. A slice is a sequence of largestcoding units. Location of largest coding unit is specified by thelargest coding unit address IcuAddr.

Each coding unit including the largest coding unit is divided into fourcoding units recursively. It results to the quadtree segmentation of thelargest coding unit. Location of coding unit is specified by the codingunit index cuIdx which designates, as a starting point, the upper-leftsample of the largest coding unit (pixel or coefficient).

Once the coding unit is not allowed to be split, it shall be consideredas the prediction unit. Similar to the coding unit, location ofprediction unit is specified by the prediction unit index puIdx whichdesignates, as a starting point, the upper-left sample of the largestcoding unit.

The prediction unit may include a plurality of partitions (predictionunit partition or sub PU). The prediction unit partition is specified byprediction unit partition index puPartIdx which designates, as astarting point, the upper-left sample of the prediction unit.

The prediction unit may include a plurality of transform units. Similarto the coding unit, transform unit may be divided into four small sizetransform units (sub transform units). This allows quadtree segmentationof the residual signal. Location of the transform unit is specified bythe transform unit index tuIdx which designates, as a starting point,the upper-left sample of the prediction unit.

Here, the definitions of the processing units are as follows.

coding tree block (CTB): A basic unit for specifying the quadtreesegmentation of the given square region. CTB can have various sizes of asquare shape.

largest coding tree block (LCTB): Coding tree block of the largest sizeallowed in the slice. A slice consists of non-overlapped LCTBs.

smallest coding tree block (SCTB): Coding tree block of the smallestsize allowed in the slice. SCTB is not allowed to be split into smallerCTBs.

prediction unit (PU): A basic unit for identifying the predictionprocess. The size of PU is the same to that of the CU which is notallowed to be split any more. PU can be split into multiple partitionswhich may have arbitrary shapes whereas CU is allowed to be split intofour square shapes.

transform unit (TU): A basic unit for identifying transform andquantization process.

coding unit (CU): Same as coding tree block.

largest coding unit (LCU): Same as largest coding tree block.

smallest coding unit (SCU): Same as smallest coding tree block.

FIG. 5 is a diagram showing a configuration a coded stream beingconsidered under HEVC standard.

In a coded stream being considered under the HEVC standard, a referenceindex is stored at each of the PUs. For example, as shown in FIG. 5, LCUis divided into four sub CUs, and each of the sub CUs has PU and TU. ThePU is further divided into four sub PUs. In this case, a reference index(ref_idex) is stored at each of the four sub PUs. In other words, theimage coding apparatus always has to transmit the reference index to theimage decoding apparatus on a PU-by-PU basis. As a result, an overheadis increased. In other words, the amount of coding of a coded stream islarge and coding efficiency is reduced.

Therefore, in the coded stream generated by the image coding apparatus1000 and decoded by the image decoding apparatus 2000 according to thepresent embodiment, the reference index common to the processing unit isstored in the processing unit which is located at a higher hierarchicallayer that is shallower than the lowest PU.

FIG. 6 is a block diagram showing a configuration of a coded streamaccording to the present embodiment.

In the coded stream, for example, as shown in FIG. 6, LCU is dividedinto four sub CUs, and each of the sub CUs has PU and TU. The PU isfurther divided into four sub PUs. In this case, in the coded streamaccording to the present embodiment, the reference index (ref_idx) isnot stored at the lowest sub PU, and the reference index common to thesub PUs is stored at the sub CU which is located at, for example, ahigher hierarchical layer that is shallower than the sub PU. With this,in the present embodiment, an overhead can be reduced and codingefficiency can be increased.

It should be noted that the reference index to be stored in the sub CUdoes not have to be a reference index common to each of the sub PUsincluded in the sub CU, and may be a set of four reference indexes foreach of the sub PUs. With this, since the reference indexes each for thesub PUs are stored in the same place as a whole, it is easier for theimage decoding apparatus 2000 to perform decoding process. Moreover, theposition in which the reference index is stored in the processing unit(sub CU) may be the head or the tail of the processing unit.

Furthermore, in the coded stream according to the present embodiment,the hierarchy depth information (maximum hierarchy depth) indicating thehierarchical layer of the lowest processing unit in which the referenceindex is stored is stored in a header such as a sequence header. Forexample, maximum hierarchy depth=2.

The image coding apparatus 1000 generates and outputs the coded stream.Meanwhile, the image decoding apparatus 2000 identifies the processingunit in which the reference index is stored (sub CU located at thesecond hierarchical layer) by parsing the hierarchy depth information(maximum hierarchy depth) stored in a header such as a sequence headerof the coded stream, and parses the reference index stored in theprocessing unit. Then, the image decoding apparatus 2000 performs interprediction by applying the reference index to the PUs included in thesub CU which stores the reference index.

FIG. 7A and FIG. 7B are each a diagram showing the storage position ofhierarchy depth information (maximum hierarchy depth).

As shown in FIG. 7A, hierarchical depth information (maximum hierarchydepth) D300 is stored in a sequence header. As shown in FIG. 7B,hierarchy depth information (maximum hierarchy depth) D302 is stored ina picture header.

FIG. 8 is a flowchart showing decoding by an image decoding apparatus2000 according to the present embodiment.

The image decoding apparatus 2000 first parses hierarchy depthinformation (maximum hierarchy depth) stored in the picture header (StepS1), and parses a flag of the CU (Step S2). Next, the image decodingapparatus 2000 divides the CU into sub CUs that are smaller than the CU,based on the parsed flag (Step S3). Then, the image decoding apparatus2000 determines hierarchical layer of the sub CU (Step S4), anddetermines whether or not the determined hierarchical layer matches thehierarchical layer indicated by hierarchy depth information (maximumhierarchy depth) (Step S5).

When it is determined that the determined hierarchical layer matches thehierarchical layer indicated by hierarchy depth information (Yes in StepS5), the image decoding apparatus 2000 parses the reference index storedin the sub CU (Step S6) and then decodes the processing unit that is thesub CU by performing inter prediction using the parsed reference index(Step S7).

Meanwhile, it is determined in Step S5 that the determined hierarchicallayer fails to match the hierarchical layer indicated by hierarchy depthinformation (No in Step S5), the image decoding apparatus 2000determines whether or not the sub CU cannot be further divided into foursmaller sub CUs, based on the parsed flag (Step S8). When it isdetermined that the sub CU can be further divided into four smaller subCUs (No in Step S8), the image decoding apparatus 2000 selects any onesub CU from the four smaller sub CUs (Step S9), and then performs theprocesses from Step S4 on the selected sub CU.

Meanwhile, when it is determined in Step S8 that the sub CU cannot befurther divided into four smaller sub CUs (Yes in Step S8), the imagedecoding apparatus 2000 parses partitioning syntax element of the subCU, that is to say, the PU (Step S10). The partitioning syntax elementshows the total number of the sub PUs and the size of the sub PU whenthe PU is divided into a plurality of sub PUs. Furthermore, the imagedecoding apparatus 2000 divides the sub CU, that is to say, PU intosmaller PUs (sub PUs), based on the parsed partitioning syntax element(Step S11). Then, the image decoding apparatus 2000 parses the referenceindexes each for the sub PU (Step S12), and then performs the process ofStep S7.

FIG. 9 is a flowchart showing coding by the image coding apparatus 1000according to the present embodiment.

The image coding apparatus 1000 first writes hierarchy depth information(maximum hierarchy depth) into a picture header (Step S21), anddetermines the best size for dividing the CU (Step S22). Next, the imagecoding apparatus 1000 writes, into the CU, flag for dividing the CU intothe processing units of the determined sizes (Step S23). Then, the imagecoding apparatus 1000 determines the hierarchical layer of theprocessing unit to be coded (CU or sub CU) (Step S24), and thendetermines whether or not the determined hierarchical layer matches thehierarchical layer indicated by the previously written hierarchy depthinformation (maximum hierarch depth) (Step S25).

When it is determined that the determined hierarchical layer matches thepreviously written hierarchy depth information (Yes in Step S25), theimage coding apparatus 1000 writes the reference indexes into theprocessing unit (CU or sub CU) (Step S26) and then codes the processingunit by performing inter prediction using the written reference indexes(Step S27). Furthermore, the image coding apparatus 1000 decodes thecoded processing unit by performing inter prediction using the writtenreference indexes (Step S28).

Meanwhile, it is determined in Step S25 that the determined hierarchicallayer fails to match the previously written hierarchy depth information(No in Step S25), the image coding apparatus 1000 determines whether ornot the processing unit cannot be further divided into four smaller subCUs, based on the parsed flag (Step S29). When it is determined that theprocessing unit can be further divided into four smaller sub CUs (No inStep S29), the image coding apparatus 1000 selects any one sub CU fromthe four smaller sub CUs (Step S30), and then performs the processesfrom Step S24 on the selected sub CU.

Meanwhile, it is determined in Step S29 that the processing unit cannotbe further divided into four smaller sub CUs (Yes in Step S29), theimage coding apparatus 1000 writes partitioning syntax element into theprocessing unit (CU or sub CU), that is to say, the PU (Step S31). Thepartitioning syntax element shows the total number of the sub PUs andthe size of the sub PU when the PU is divided into a plurality of subPUs. Furthermore, the image coding apparatus 1000 divides the processingunit, that is to say, the PU into smaller PUs (sub PUs), based on thewritten partitioning syntax element (Step S32). Then, the image codingapparatus 1000 writes the reference index into each of the sub PUs (StepS33), and then performs the processes from Step S27.

As described above, the image coding apparatus 1000 according to thepresent embodiment transmits hierarchy depth information (maximumhierarchy depth) by including it in a header such as a picture header.Then, when the hierarchical layer of the lowest CU (sub CU) is higherthan the hierarchical layer indicated by maximum hierarchy depth, theimage coding apparatus 1000 individually transmits the reference indexcorresponding to each PU included in the CU (sub CU). When thehierarchical layer of the lowest CU (sub CU) is equal to thehierarchical layer indicated by maximum hierarchy depth or deeper thanthe hierarchical layer indicated by maximum hierarch depth, the imagecoding apparatus 1000 transmits combined ref_idx in association with theCU (sub CU) of the hierarchical layer indicated by maximum hierarchydepth. The combined ref_idx is a reference index to be applied to allPUs included in the CU (sub CU).

It should be noted that when the hierarchical layer of the lowest CU isdeeper than or equal to the hierarchical layer indicated by maximumhierarchy depth, the image coding apparatus 1000 according to thepresent embodiment, as described above, writes the reference index intothe CU (sub CU) of the hierarchical layer indicated by maximum hierarchydepth, but may write the reference index into the CU (sub CU) locatedhigher than the hierarchical layer. In this case, the image decodingapparatus 2000 parses the reference index stored in the CU (sub CU)located higher than the hierarchical layer indicated by the maximumhierarchy depth.

As described above, in the image coding method according to the presentembodiment, by not repeatedly writing the same reference index into aplurality of small prediction units, only one reference index is writteninto a large processing unit which is located at a higher hierarchicallayer than the prediction units and includes the prediction units.Therefore, the redundancy of the reference index can be removed andcoding efficiency can be increased. Moreover, since the image decodingapparatus 2000 identifies the hierarchical layer having the processingunit in which the reference index is stored, by parsing hierarchy depthinformation, the image decoding apparatus 2000 can reduce the processingload of searching the processing unit in which the reference index isstored and can appropriately decode a coded stream generated by theimage coding apparatus 1000.

[Variation 1]

An image coding apparatus 1000 according to Variation 1 of the presentembodiment sends the first flag by including it in a header such as apicture header. The first flag shows whether or not combined ref_idx isstored in the lowest CU (sub CU). In other words, the image codingapparatus 1000 sends combined ref_idx in association with the CU (subCU) when the storage of combined ref_idx is indicated by the first flag.In other words, independently of the size of the CU (sub CU), combinedref_idx common to all the PUs included in the CU (sub CU) is sent.Meanwhile, when the storage of combined ref_idx is not indicated by thefirst flag, the image coding apparatus 1000 individually sends thereference index corresponding to each of the PUs included in the CU (subCU). In other words, independently of the size for each of the PUs, anindividual reference index for each of the PUs is sent.

FIG. 10 is a flowchart showing decoding by the image decoding apparatus2000 according to Variation 1 of the present embodiment.

The image decoding apparatus 2000 first parses the first flag stored ina picture header (Step S41), and further parses the second flag storedin the CU (Step S42). Next, the image decoding apparatus 2000 dividesthe CU into sub CUs that are smaller than the CU, based on the parsedsecond flag (Step S43). Then, the image decoding apparatus 2000determines whether or not the sub CU cannot be further divided into foursmaller sub CUs, based on the parsed second flag (Step S44). When it isdetermined that the sub CU can be further divided into four smaller subCUs (No in Step S44), the image decoding apparatus 2000 selects any onesub CU from the four smaller sub CUs (Step S45), and then performs theprocesses from Step S43 on the selected sub CU. Meanwhile, when it isdetermined that the sub CU cannot be further divided into four smallersub CUs (Yes in Step S44), the image decoding apparatus 2000 furtherdetermines whether or not the first flag parsed in Step S41 indicatesparsing of the reference index in the lowest CU (sub CU) (Step S46).

When it is determined that the first flag indicates parsing of thereference index in the lowest CU (sub CU) (Yes in Step S46), the imagedecoding apparatus 2000 parses the reference index for the lowest CU(sub CU) (Step S47) and decodes the processing unit that is the CU (subCU) by performing inter prediction using the parsed reference index(Step S48).

Meanwhile, when it is determined in Step S46 that the first flag failsto indicate parsing of the reference index in the lowest CU (sub CU) (Noin Step S46), the image decoding apparatus 2000 parses partitioningsyntax element of the lowest CU (sub CU), that is to say, PU (Step S49).The partitioning syntax element shows the total number of the sub PUsand the size of the sub PU when the PU is divided into a plurality ofsub PUs. Furthermore, the image decoding apparatus 2000 divides thelowest CU (sub CU), that is to say, the PU into PUs that are smallerthan the PU (sub PUs), based on the parsed partitioning syntax element(Step S50). Then, the image decoding apparatus 2000 parses the referenceindexes each for the sub PU (Step S51), and then performs the process ofStep S48.

[Variation 2]

The image coding apparatus 1000 according to the above describedembodiment stores reference indexes to be applied to the sub PUs, in aprocessing unit located in a higher hierarchical layer (for example, CUor sub CU) including a plurality of sub PUs. Moreover, the imagedecoding apparatus 2000 according to the above described embodimentparses reference index stored in the processing unit located in thehigher hierarchical layer, and applies the reference index to the abovedescribed PUs.

Conversely, an image coding apparatus 1000 according to the presentvariation stores the reference index to be applied to the sub PUs in aprocessing unit located in a higher hierarchical layer including aplurality of sub PUs, and stores adaptive motion vector resolutionswitch flag (also referred to as Motion Vector Resolution Flag, mvres,MVres, or MVRes). Moreover, the image decoding apparatus 2000 accordingto the present variation parses the reference index and adaptive motionvector resolution switch flag, and applies the reference index and theadaptive motion vector resolution switch flag to the above described subPUs.

It should be noted that the adaptive motion vector resolution switchflag is a flag for switching the motion vector resolution between ⅛pixel resolution and ¼ pixel resolution.

FIG. 11 is a flowchart showing decoding of PU by the image decodingapparatus 2000 according to the present variation.

First, the image decoding apparatus 2000 parses syntax elements of PUand derives a prediction mode (Step S61). Then, the image decodingapparatus 2000 determines whether or not the prediction mode is interprediction (Step S62). When it is determined that the prediction mode isnot inter prediction (No in Step S62), the image decoding apparatus 2000parses syntax element related to the prediction mode (Step S63).Meanwhile, it is determined that the prediction mode is inter prediction(Yes in Step S62), the image decoding apparatus 2000 parses the syntaxand derives the total number of PUs (sub PUs) included in the PU(numPUParts) and the sizes of the PUs (currPUSize[numPUParts]) (StepS64).

Next, the image decoding apparatus 2000 performs the processes of StepsS66 to S71 on each of the derived number of PUs. More specifically, theimage decoding apparatus 2000 parses merge flag (merge_flag[i],merge_left_flag[i]) and/or inter_pred_idc[i] (Step S66), and determineswhether or not PU is not merged (PU cannot be further divided) and thesize of PU is smaller than MinRefIdxUnit (Step S67). When it isdetermined that the PU is not merged and the size of PU is smaller thanMinRefIdxUnit (Yes in Step S67), the image decoding apparatus 2000parses the reference indexes (ref_idx_l0[i], ref_idx_l1[i]) stored inthe PU (Step S68). Furthermore, the image decoding apparatus 2000determines whether or not the PU is not merged and the size of PU issmaller than MinMVResUnit (Step S69). When it is determined that the PUis not merged and the size of PU is smaller than MinMVResUnit (Yes inStep S69), the image decoding apparatus 2000 parses the adaptive motionvector resolution switch flag (mvres_l0[i], mvres_l1[i]) stored in thePU (Step S70). Furthermore, the image decoding apparatus 2000 parses adifference motion vector (mvd_l0[i], mvd_l1[i]) and mvp_idx(mvp_idx_l0[i], mvp_idx_l1[i]) (Step S71).

Next, the image decoding apparatus 2000 determines whether or not thesize of the CU to be decoded (currCUSize) is larger than or equal toMinRefIdxUnit and at least one PU is not merged (Step S72). When it isdetermined that the size of CU to be decoded is larger than or equal toMinRefIdxUnit and at least one PU is not merged (Yes in Step S72), theimage decoding apparatus 2000 parses a reference index of the CU to bedecoded (cu_ref_idx_l0, cu_ref_idx_l1) (Step S73). Furthermore, theimage decoding apparatus 2000 determines whether or not the size of theCU to be decoded is larger than or equal to MinMVResUnit and at leastone PU is not merged (Step S74). When it is determined that the size ofthe CU to be decoded is larger than or equal to MinMVResUnit and atleast one CU is not merged (Yes in Step S74), the image decodingapparatus 2000 parses adaptive motion vector resolution switch flag ofthe CU to be decoded (cu_mvres_l0, cu_mvres_l1) (Step S75).

The image decoding method and the image coding method according to thepresent invention have been described using the above describedembodiment and variations. However, the present invention is not definedonly by these.

For example, the image decoding method according to the above describedEmbodiment 1 and the variation includes the processes of Steps S2 andS4, and the like in FIG. 8. However, the present invention can obtainthe above described effect without the processes.

FIG. 12A is a flowchart showing the image decoding method according tothe present invention.

The image decoding method according to the present invention is an imagedecoding method for decoding a coded stream which includes a pluralityof processing units and a header of the processing units, the codedstream being generated by coding a moving picture using interprediction. Here, the processing units includes at least one processingunit divided into a plurality of sub processing units in a hierarchywhich decrease in size from a higher level to a lower level, and thehierarchy includes: a highest hierarchical layer in which a coding unitexists as a largest processing unit; and a lower hierarchical layerwhich is deeper than the highest hierarchical layer and in which aprediction unit exists as a processing unit smaller than the codingunit. In the image decoding method, by parsing hierarchy depthinformation stored in the header and indicating a hierarchical layerhigher than a lowest hierarchical layer in which a smallest predictionunit exits, a hierarchical layer is identified which is indicated by thehierarchy depth information or a hierarchical layer higher than theindicated hierarchical layer, the hierarchical layer having a predictionunit in which a reference index necessary for decoding is stored (StepS101) Next, the prediction unit is decoded using the reference indexstored in the prediction unit at the identified hierarchical layer (StepS102).

By performing the processes of Steps S101 and S102, the same effect asthat of Embodiment 1 can be obtained. The other processes are notessential for the present invention. Moreover, the image decodingapparatus according to the present invention can obtain the same effectas that of Embodiment 1 by including structural elements which performthe processes of Steps S101 and S102. The other structural elements arenot essential for the present invention. It should be noted that in theimage decoding apparatus 2000 according to Embodiment 1, the decodingprocessing unit 2200 perform the process of Step S101 and the decodingprocessing unit 2100 performs the process of Step S102.

Moreover, the image coding method according to the above describedEmbodiment 1 and the variation includes the processes of Step S22 andthe like in FIG. 9. However, the present invention can obtain the abovedescribed effect without the processes.

FIG. 12B is a flowchart showing the image coding method according to thepresent invention.

The image coding method according to the present invention is an imagecoding method for generating a coded stream which includes a pluralityof processing units and a header of the processing units, by coding amoving picture using inter prediction. Here, the processing unitsincludes at least one processing unit divided into a plurality of subprocessing units in a hierarchy which decrease in size from a higherlevel to a lower level, and the hierarchy includes: a highesthierarchical layer in which a coding unit exists as a largest processingunit; and a lower hierarchical layer which is deeper than the highesthierarchical layer and in which a prediction unit exists as a processingunit smaller than the coding unit. In the image coding method, themoving picture is coded using inter prediction (Step S111). Next,hierarchy depth information which is information for identifying ahierarchical layer having a prediction unit in which a reference indexnecessary for decoding is stored and indicates a hierarchical layerhigher than a lowest hierarchical layer in which a smallest predictionunit exists is written into the header (Step S112). Next, the referenceindex to be applied to the prediction unit is written into a predictionunit located at a hierarchical layer indicated by the hierarchy depthinformation or located higher than the indicated hierarchical layer.(Step S113)

By performing the processes of Steps S111 to S113, the same effect asthat of Embodiment 1 can be obtained. The other processes are notessential for the present invention. Moreover, the image codingapparatus according to the present invention can obtain the same effectas that of Embodiment 1 by including structural elements which performthe processes of Steps S111 to S113. The other structural elements arenot essential for the present invention. It should be noted that in theimage coding apparatus 1000 according to Embodiment 1, the entropycoding unit 1104 performs the processes of Steps S111 to S113, based onthe control by the coding control unit 1200.

It should be noted that a syntax of a header according to the presentinvention is shown in FIGS. 13A to 13C. The syntax of the processingunit according to the present invention (CU, PU, and TU) are shown inFIGS. 14A to 14C.

FIG. 13A is a diagram showing a syntax of a sequence header. In thesequence header, for example, the maximum number of reference framesthat can be referred (max_num_ref_frames), the size of the picture(pic_width_in_luma_samples, pic_height_in_luma_samples), and the likeare defined.

FIG. 13B is a diagram showing a syntax of a picture header. In thepicture header, as shown in part d1 of the syntax, the number ofreference indexes to be held for each reference direction (forwarddirection and backward direction) is defined, and an initial QP (numberobtained by subtracting 26 from the initial QP) is defined.

FIG. 13C is a diagram showing a syntax of a slice header. The sliceheader, as shown in part d2 of the syntax, is configured such that thenumber of the above described reference indexes to be held can berewritten for each slice. Moreover, the slice header, as shown inanother part d3 of the syntax, defines the difference value of QP fromthe initial QP which is defined by the above described picture header.

FIG. 14A is a diagram showing a syntax of CU. In the CU, as shown inparts d4 and d5 of the syntax, PU and TU for the CU are defined.

FIG. 14B is a diagram showing a syntax of PU. The PU has, as shown inparts d6 and d8 of the syntax, a reference index for each referencedirection, and has, as shown in other parts d7 and d9 of the syntax,adaptive motion vector resolution switch flag (mvres) for each referencedirection.

FIG. 14C is a diagram showing a syntax of TU. The TU has, as shown inpart d10 of the syntax, coefficients (transform coefficients) in whichorthogonal transform and quantization are performed on the differenceimage.

[Embodiment 2]

The processing described in each of embodiments can be simplyimplemented in an independent computer system, by recording, in arecording medium, a program for implementing the configurations of theimage coding method and the image decoding method described in each ofembodiments. The recording media may be any recording media as long asthe program can be recorded, such as a magnetic disk, an optical disk, amagnetic optical disk, an IC card, and a semiconductor memory.

Hereinafter, the applications to the image coding method and the imagedecoding method described in each of embodiments and systems usingthereof will be described.

FIG. 15 illustrates an overall configuration of a content providingsystem ex100 for implementing content distribution services. The areafor providing communication services is divided into cells of desiredsize, and base stations ex106, ex107, ex108, ex109, and ex110 which arefixed wireless stations are placed in each of the cells.

The content providing system ex100 is connected to devices, such as acomputer ex111, a personal digital assistant (PDA) ex112, a cameraex113, a cellular phone ex114 and a game machine ex115, via the Internetex101, an Internet service provider ex102, a telephone network ex104, aswell as the base stations ex106 to ex110, respectively.

However, the configuration of the content providing system ex100 is notlimited to the configuration shown in FIG. 15, and a combination inwhich any of the elements are connected is acceptable. In addition, eachdevice may be directly connected to the telephone network ex104, ratherthan via the base stations ex106 to ex110 which are the fixed wirelessstations. Furthermore, the devices may be interconnected to each othervia a short distance wireless communication and others.

The camera ex113, such as a digital video camera, is capable ofcapturing video. A camera ex116, such as a digital camera, is capable ofcapturing both still images and video. Furthermore, the cellular phoneex114 may be the one that meets any of the standards such as GlobalSystem for Mobile Communications (GSM) (registered trademark), CodeDivision Multiple Access (CDMA), Wideband-Code Division Multiple Access(W-CDMA), Long Term Evolution (LTE), and High Speed Packet Access(HSPA). Alternatively, the cellular phone ex114 may be a PersonalHandyphone System (PHS).

In the content providing system ex100, a streaming server ex103 isconnected to the camera ex113 and others via the telephone network ex104and the base station ex109, which enables distribution of images of alive show and others. In such a distribution, a content (for example,video of a music live show) captured by the user using the camera ex113is coded as described above in each of embodiments, and the codedcontent is transmitted to the streaming server ex103. On the other hand,the streaming server ex103 carries out stream distribution of thetransmitted content data to the clients upon their requests. The clientsinclude the computer ex111, the PDA ex112, the camera ex113, thecellular phone ex114, and the game machine ex115 that are capable ofdecoding the above-mentioned coded data. Each of the devices that havereceived the distributed data decodes and reproduces the coded data.

The captured data may be coded by the camera ex113 or the streamingserver ex103 that transmits the data, or the coding processes may beshared between the camera ex113 and the streaming server ex103.Similarly, the distributed data may be decoded by the clients or thestreaming server ex103, or the decoding processes may be shared betweenthe clients and the streaming server ex103. Furthermore, the data of thestill images and video captured by not only the camera ex113 but alsothe camera ex116 may be transmitted to the streaming server ex103through the computer ex111. The coding processes may be performed by thecamera ex116, the computer ex111, or the streaming server ex103, orshared among them.

Furthermore, the coding and decoding processes may be performed by anLSI ex500 generally included in each of the computer ex111 and thedevices. The LSI ex500 may be configured of a single chip or a pluralityof chips. Software for coding and decoding video may be integrated intosome type of a recording medium (such as a CD-ROM, a flexible disk, anda hard disk) that is readable by the computer ex111 and others, and thecoding and decoding processes may be performed using the software.Furthermore, when the cellular phone ex114 is equipped with a camera,the video data obtained by the camera may be transmitted. The video datais data coded by the LSI ex500 included in the cellular phone ex114.

Furthermore, the streaming server ex103 may be composed of servers andcomputers, and may decentralize data and process the decentralized data,record, or distribute data.

As described above, the clients may receive and reproduce the coded datain the content providing system ex100. In other words, the clients canreceive and decode information transmitted by the user, and reproducethe decoded data in real time in the content providing system ex100, sothat the user who does not have any particular right and equipment canimplement personal broadcasting.

Aside from the example of the content providing system ex100, at leastone of the image coding apparatus and the image decoding apparatusdescribed in each of embodiments may be implemented in a digitalbroadcasting system ex200 illustrated in FIG. 16. More specifically, abroadcast station ex201 communicates or transmits, via radio waves to abroadcast satellite ex202, multiplexed data obtained by multiplexingaudio data and others onto video data. The video data is data coded bythe image coding method described in each of embodiments. Upon receiptof the multiplexed data, the broadcast satellite ex202 transmits radiowaves for broadcasting. Then, a home-use antenna ex204 with a satellitebroadcast reception function receives the radio waves. Next, a devicesuch as a television (receiver) ex300 and a set top box (STB) ex217decodes the received multiplexed data, and reproduces the decoded data.

Furthermore, a reader/recorder ex218 (i) reads and decodes themultiplexed data recorded on a recording medium ex215, such as a DVD anda BD, or (i) codes video signals in the recording medium ex215, and insome cases, writes data obtained by multiplexing an audio signal on thecoded data. The reader/recorder ex218 can include the image decodingapparatus or the image coding apparatus as shown in each of embodiments.In this case, the reproduced video signals are displayed on the monitorex219, and can be reproduced by another device or system using therecording medium ex215 on which the multiplexed data is recorded. It isalso possible to implement the moving picture decoding apparatus in theset top box ex217 connected to the cable ex203 for a cable television orto the antenna ex204 for satellite and/or terrestrial broadcasting, soas to display the video signals on the monitor ex219 of the televisionex300. The moving picture decoding apparatus may be implemented not inthe set top box but in the television ex300.

FIG. 17 illustrates the television (receiver) ex300 that uses the imagecoding method and the image decoding method described in each ofembodiments. The television ex300 includes: a tuner ex301 that obtainsor provides multiplexed data obtained by multiplexing audio data ontovideo data, through the antenna ex204 or the cable ex203, etc. thatreceives a broadcast; a modulation/demodulation unit ex302 thatdemodulates the received multiplexed data or modulates data intomultiplexed data to be supplied outside; and amultiplexing/demultiplexing unit ex303 that demultiplexes the modulatedmultiplexed data into video data and audio data, or multiplexes videodata and audio data coded by a signal processing unit ex306 into data.

The television ex300 further includes: a signal processing unit ex306including an audio signal processing unit ex304 and a video signalprocessing unit ex305 that decode audio data and video data and codeaudio data and video data, respectively; and an output unit ex309including a speaker ex307 that provides the decoded audio signal, and adisplay unit ex308 that displays the decoded video signal, such as adisplay. Furthermore, the television ex300 includes an interface unitex317 including an operation input unit ex312 that receives an input ofa user operation. Furthermore, the television ex300 includes a controlunit ex310 that controls overall each constituent element of thetelevision ex300, and a power supply circuit unit ex311 that suppliespower to each of the elements. Other than the operation input unitex312, the interface unit ex317 may include: a bridge ex313 that isconnected to an external device, such as the reader/recorder ex218; aslot unit ex314 for enabling attachment of the recording medium ex216,such as an SD card; a driver ex315 to be connected to an externalrecording medium, such as a hard disk; and a modem ex316 to be connectedto a telephone network. Here, the recording medium ex216 canelectrically record information using a non-volatile/volatilesemiconductor memory element for storage. The constituent elements ofthe television ex300 are connected to each other through a synchronousbus.

First, the configuration in which the television ex300 decodesmultiplexed data obtained from outside through the antenna ex204 andothers and reproduces the decoded data will be described. In thetelevision ex300, upon a user operation through a remote controllerex220 and others, the multiplexing/demultiplexing unit ex303demultiplexes the multiplexed data demodulated by themodulation/demodulation unit ex302, under control of the control unitex310 including a CPU. Furthermore, the audio signal processing unitex304 decodes the demultiplexed audio data, and the video signalprocessing unit ex305 decodes the demultiplexed video data, using thedecoding method described in each of embodiments, in the televisionex300. The output unit ex309 provides the decoded video signal and audiosignal outside, respectively. When the output unit ex309 provides thevideo signal and the audio signal, the signals may be temporarily storedin buffers ex318 and ex319, and others so that the signals arereproduced in synchronization with each other. Furthermore, thetelevision ex300 may read multiplexed data not through a broadcast andothers but from the recording media ex215 and ex216, such as a magneticdisk, an optical disk, and a SD card. Next, a configuration in which thetelevision ex300 codes an audio signal and a video signal, and transmitsthe data outside or writes the data on a recording medium will bedescribed. In the television ex300, upon a user operation through theremote controller ex220 and others, the audio signal processing unitex304 codes an audio signal, and the video signal processing unit ex305codes a video signal, under control of the control unit ex310 using thecoding method described in each of embodiments. Themultiplexing/demultiplexing unit ex303 multiplexes the coded videosignal and audio signal, and provides the resulting signal outside. Whenthe multiplexing/demultiplexing unit ex303 multiplexes the video signaland the audio signal, the signals may be temporarily stored in thebuffers ex320 and ex321, and others so that the signals are reproducedin synchronization with each other. Here, the buffers ex318, ex319,ex320, and ex321 may be plural as illustrated, or at least one buffermay be shared in the television ex300. Furthermore, data may be storedin a buffer so that the system overflow and underflow may be avoidedbetween the modulation/demodulation unit ex302 and themultiplexing/demultiplexing unit ex303, for example.

Furthermore, the television ex300 may include a configuration forreceiving an AV input from a microphone or a camera other than theconfiguration for obtaining audio and video data from a broadcast or arecording medium, and may code the obtained data. Although thetelevision ex300 can code, multiplex, and provide outside data in thedescription, it may be capable of only receiving, decoding, andproviding outside data but not the coding, multiplexing, and providingoutside data.

Furthermore, when the reader/recorder ex218 reads or writes multiplexeddata from or on a recording medium, one of the television ex300 and thereader/recorder ex218 may decode or code the multiplexed data, and thetelevision ex300 and the reader/recorder ex218 may share the decoding orcoding.

As an example, FIG. 18 illustrates a configuration of an informationreproducing/recording unit ex400 when data is read or written from or onan optical disk. The information reproducing/recording unit ex400includes constituent elements ex401, ex402, ex403, ex404, ex405, ex406,and ex407 to be described hereinafter. The optical head ex401 irradiatesa laser spot in a recording surface of the recording medium ex215 thatis an optical disk to write information, and detects reflected lightfrom the recording surface of the recording medium ex215 to read theinformation. The modulation recording unit ex402 electrically drives asemiconductor laser included in the optical head ex401, and modulatesthe laser light according to recorded data. The reproductiondemodulating unit ex403 amplifies a reproduction signal obtained byelectrically detecting the reflected light from the recording surfaceusing a photo detector included in the optical head ex401, anddemodulates the reproduction signal by separating a signal componentrecorded on the recording medium ex215 to reproduce the necessaryinformation. The buffer ex404 temporarily holds the information to berecorded on the recording medium ex215 and the information reproducedfrom the recording medium ex215. The disk motor ex405 rotates therecording medium ex215. The servo control unit ex406 moves the opticalhead ex401 to a predetermined information track while controlling therotation drive of the disk motor ex405 so as to follow the laser spot.The system control unit ex407 controls overall the informationreproducing/recording unit ex400. The reading and writing processes canbe implemented by the system control unit ex407 using variousinformation stored in the buffer ex404 and generating and adding newinformation as necessary, and by the modulation recording unit ex402,the reproduction demodulating unit ex403, and the servo control unitex406 that record and reproduce information through the optical headex401 while being operated in a coordinated manner. The system controlunit ex407 includes, for example, a microprocessor, and executesprocessing by causing a computer to execute a program for read andwrite.

Although the optical head ex401 irradiates a laser spot in thedescription, it may perform high-density recording using near fieldlight.

FIG. 19 illustrates the recording medium ex215 that is the optical disk.On the recording surface of the recording medium ex215, guide groovesare spirally formed, and an information track ex230 records, in advance,address information indicating an absolute position on the diskaccording to change in a shape of the guide grooves. The addressinformation includes information for determining positions of recordingblocks ex231 that are a unit for recording data. Reproducing theinformation track ex230 and reading the address information in anapparatus that records and reproduces data can lead to determination ofthe positions of the recording blocks. Furthermore, the recording mediumex215 includes a data recording area ex233, an inner circumference areaex232, and an outer circumference area ex234. The data recording areaex233 is an area for use in recording the user data. The innercircumference area ex232 and the outer circumference area ex234 that areinside and outside of the data recording area ex233, respectively arefor specific use except for recording the user data. The informationreproducing/recording unit 400 reads and writes coded audio, coded videodata, or multiplexed data obtained by multiplexing the coded audio andvideo data, from and on the data recording area ex233 of the recordingmedium ex215.

Although an optical disk having a layer, such as a DVD and a BD isdescribed as an example in the description, the optical disk is notlimited to such, and may be an optical disk having a multilayerstructure and capable of being recorded on a part other than thesurface. Furthermore, the optical disk may have a structure formultidimensional recording/reproduction, such as recording ofinformation using light of colors with different wavelengths in the sameportion of the optical disk and for recording information havingdifferent layers from various angles.

Furthermore, a car ex210 having an antenna ex205 can receive data fromthe satellite ex202 and others, and reproduce video on a display devicesuch as a car navigation system ex211 set in the car ex210, in thedigital broadcasting system ex200. Here, a configuration of the carnavigation system ex211 will be a configuration, for example, includinga GPS receiving unit from the configuration illustrated in FIG. 17. Thesame will be true for the configuration of the computer ex111, thecellular phone ex114, and others.

FIG. 20A illustrates the cellular phone ex114 that uses the image codingmethod and the image decoding method described in embodiments. Thecellular phone ex114 includes: an antenna ex350 for transmitting andreceiving radio waves through the base station ex110; a camera unitex365 capable of capturing moving and still images; and a display unitex358 such as a liquid crystal display for displaying the data such asdecoded video captured by the camera unit ex365 or received by theantenna ex350. The cellular phone ex114 further includes: a main bodyunit including an operation key unit ex366; an audio output unit ex357such as a speaker for output of audio; an audio input unit ex356 such asa microphone for input of audio; a memory unit ex367 for storingcaptured video or still pictures, recorded audio, coded or decoded dataof the received video, the still pictures, e-mails, or others; and aslot unit ex364 that is an interface unit for a recording medium thatstores data in the same manner as the memory unit ex367.

Next, an example of a configuration of the cellular phone ex114 will bedescribed with reference to FIG. 20B. In the cellular phone ex114, amain control unit ex360 designed to control overall each unit of themain body including the display unit ex358 as well as the operation keyunit ex366 is connected mutually, via a synchronous bus ex370, to apower supply circuit unit ex361, an operation input control unit ex362,a video signal processing unit ex355, a camera interface unit ex363, aliquid crystal display (LCD) control unit ex359, amodulation/demodulation unit ex352, a multiplexing/demultiplexing unitex353, an audio signal processing unit ex354, the slot unit ex364, andthe memory unit ex367.

When a call-end key or a power key is turned ON by a user's operation,the power supply circuit unit ex361 supplies the respective units withpower from a battery pack so as to activate the cell phone ex114.

In the cellular phone ex114, the audio signal processing unit ex354converts the audio signals collected by the audio input unit ex356 invoice conversation mode into digital audio signals under the control ofthe main control unit ex360 including a CPU, ROM, and RAM. Then, themodulation/demodulation unit ex352 performs spread spectrum processingon the digital audio signals, and the transmitting and receiving unitex351 performs digital-to-analog conversion and frequency conversion onthe data, so as to transmit the resulting data via the antenna ex350.Also, in the cellular phone ex114, the transmitting and receiving unitex351 amplifies the data received by the antenna ex350 in voiceconversation mode and performs frequency conversion and theanalog-to-digital conversion on the data. Then, themodulation/demodulation unit ex352 performs inverse spread spectrumprocessing on the data, and the audio signal processing unit ex354converts it into analog audio signals, so as to output them via theaudio output unit ex357.

Furthermore, when an e-mail in data communication mode is transmitted,text data of the e-mail inputted by operating the operation key unitex366 and others of the main body is sent out to the main control unitex360 via the operation input control unit ex362. The main control unitex360 causes the modulation/demodulation unit ex352 to perform spreadspectrum processing on the text data, and the transmitting and receivingunit ex351 performs the digital-to-analog conversion and the frequencyconversion on the resulting data to transmit the data to the basestation ex110 via the antenna ex350. When an e-mail is received,processing that is approximately inverse to the processing fortransmitting an e-mail is performed on the received data, and theresulting data is provided to the display unit ex358.

When video, still images, or video and audio in data communication modeis or are transmitted, the video signal processing unit ex355 compressesand codes video signals supplied from the camera unit ex365 using themoving picture coding method shown in each of embodiments, and transmitsthe coded video data to the multiplexing/demultiplexing unit ex353. Incontrast, during when the camera unit ex365 captures video, stillimages, and others, the audio signal processing unit ex354 codes audiosignals collected by the audio input unit ex356, and transmits the codedaudio data to the multiplexing/demultiplexing unit ex353.

The multiplexing/demultiplexing unit ex353 multiplexes the coded videodata supplied from the video signal processing unit ex355 and the codedaudio data supplied from the audio signal processing unit ex354, using apredetermined method. Then, the modulation/demodulation unit(modulation/demodulation circuit unit) ex352 performs spread spectrumprocessing on the multiplexed data, and the transmitting and receivingunit ex351 performs digital-to-analog conversion and frequencyconversion on the data so as to transmit the resulting data via theantenna ex350.

When receiving data of a video file which is linked to a Web page andothers in data communication mode or when receiving an e-mail with videoand/or audio attached, in order to decode the multiplexed data receivedvia the antenna ex350, the multiplexing/demultiplexing unit ex353demultiplexes the multiplexed data into a video data bit stream and anaudio data bit stream, and supplies the video signal processing unitex355 with the coded video data and the audio signal processing unitex354 with the coded audio data, through the synchronous bus ex370. Thevideo signal processing unit ex355 decodes the video signal using animage decoding method corresponding to the image coding method shown ineach of embodiments, and then the display unit ex358 displays, forinstance, the video and still images included in the video file linkedto the Web page via the LCD control unit ex359. Furthermore, the audiosignal processing unit ex354 decodes the audio signal, and the audiooutput unit ex357 provides the audio.

Furthermore, similarly to the television ex300, a terminal such as thecellular phone ex114 probably have 3 types of implementationconfigurations including not only (i) a transmitting and receivingterminal including both a coding apparatus and a decoding apparatus, butalso (ii) a transmitting terminal including only a coding apparatus and(iii) a receiving terminal including only a decoding apparatus. Althoughthe digital broadcasting system ex200 receives and transmits themultiplexed data obtained by multiplexing audio data onto video data inthe description, the multiplexed data may be data obtained bymultiplexing not audio data but character data related to video ontovideo data, and may be not multiplexed data but video data itself.

As such, the moving picture coding method and the moving picturedecoding method in each of embodiments can be used in any of the devicesand systems described. Thus, the advantages described in each ofembodiments can be obtained.

Furthermore, the present invention is not limited to embodiments, andvarious modifications and revisions are possible without departing fromthe scope of the present invention.

[Embodiment 3]

Video data can be generated by switching, as necessary, between (i) themoving picture coding method or the moving picture coding apparatusshown in each of embodiments and (ii) a moving picture coding method ora moving picture coding apparatus in conformity with a differentstandard, such as MPEG-2, MPEG-4 AVC, and VC-1.

Here, when a plurality of video data that conforms to the differentstandards is generated and is then decoded, the decoding methods need tobe selected to conform to the different standards. However, since towhich standard each of the plurality of the video data to be decodedconform cannot be detected, there is a problem that an appropriatedecoding method cannot be selected.

In order to solve the problem, multiplexed data obtained by multiplexingaudio data and others onto video data has a structure includingidentification information indicating to which standard the video dataconforms. The specific structure of the multiplexed data including thevideo data generated in the moving picture coding method and by themoving picture coding apparatus shown in each of embodiments will behereinafter described. The multiplexed data is a digital stream in theMPEG-2 Transport Stream format.

FIG. 21 illustrates a structure of the multiplexed data. As illustratedin FIG. 21, the multiplexed data can be obtained by multiplexing atleast one of a video stream, an audio stream, a presentation graphicsstream (PG), and an interactive graphics stream. The video streamrepresents primary video and secondary video of a movie, the audiostream (IG) represents a primary audio part and a secondary audio partto be mixed with the primary audio part, and the presentation graphicsstream represents subtitles of the movie. Here, the primary video isnormal video to be displayed on a screen, and the secondary video isvideo to be displayed on a smaller window in the primary video.Furthermore, the interactive graphics stream represents an interactivescreen to be generated by arranging the GUI components on a screen. Thevideo stream is coded in the image coding method or by the image codingapparatus shown in each of embodiments, or in a moving picture codingmethod or by a moving picture coding apparatus in conformity with aconventional standard, such as MPEG-2, MPEG-4 AVC, and VC-1. The audiostream is coded in accordance with a standard, such as Dolby-AC-3, DolbyDigital Plus, MLP, DTS, DTS-HD, and linear PCM.

Each stream included in the multiplexed data is identified by PID. Forexample, 0x1011 is allocated to the video stream to be used for video ofa movie, 0x1100 to 0x111F are allocated to the audio streams, 0x1200 to0x121F are allocated to the presentation graphics streams, 0x1400 to0x141F are allocated to the interactive graphics streams, 0x1B00 to0x1B1F are allocated to the video streams to be used for secondary videoof the movie, and 0x1A00 to 0x1A1F are allocated to the audio streams tobe used for the secondary audio to be mixed with the primary audio.

FIG. 22 schematically illustrates how data is multiplexed. First, avideo stream ex235 composed of video frames and an audio stream ex238composed of audio frames are transformed into a stream of PES packetsex236 and a stream of PES packets ex239, and further into TS packetsex237 and TS packets ex240, respectively. Similarly, data of apresentation graphics stream ex241 and data of an interactive graphicsstream ex244 are transformed into a stream of PES packets ex242 and astream of PES packets ex245, and further into TS packets ex243 and TSpackets ex246, respectively. These TS packets are multiplexed into astream to obtain multiplexed data ex247.

FIG. 23 illustrates how a video stream is stored in a stream of PESpackets in more detail. The first bar in FIG. 23 shows a video framestream in a video stream. The second bar shows the stream of PESpackets. As indicated by arrows denoted as yy1, yy2, yy3, and yy4 inFIG. 23, the video stream is divided into pictures as I pictures, Bpictures, and P pictures each of which is a video presentation unit, andthe pictures are stored in a payload of each of the PES packets. Each ofthe PES packets has a PES header, and the PES header stores aPresentation Time-Stamp (PTS) indicating a display time of the picture,and a Decoding Time-Stamp (DTS) indicating a decoding time of thepicture.

FIG. 24 illustrates a format of TS packets to be finally written on themultiplexed data. Each of the TS packets is a 188-byte fixed lengthpacket including a 4-byte TS header having information, such as a PIDfor identifying a stream and a 184-byte TS payload for storing data. ThePES packets are divided, and stored in the TS payloads, respectively.When a BD ROM is used, each of the TS packets is given a 4-byteTP_Extra_Header, thus resulting in 192-byte source packets. The sourcepackets are written on the multiplexed data. The TP_Extra_Header storesinformation such as an Arrival_Time_Stamp (ATS). The ATS shows atransfer start time at which each of the TS packets is to be transferredto a PID filter. The source packets are arranged in the multiplexed dataas shown at the bottom of FIG. 24. The numbers incrementing from thehead of the multiplexed data are called source packet numbers (SPNs).

Each of the TS packets included in the multiplexed data includes notonly streams of audio, video, subtitles and others, but also a ProgramAssociation Table (PAT), a Program Map Table (PMT), and a Program ClockReference (PCR). The PAT shows what a PID in a PMT used in themultiplexed data indicates, and a PID of the PAT itself is registered aszero. The PMT stores PIDs of the streams of video, audio, subtitles andothers included in the multiplexed data, and attribute information ofthe streams corresponding to the PIDs. The PMT also has variousdescriptors relating to the multiplexed data. The descriptors haveinformation such as copy control information showing whether copying ofthe multiplexed data is permitted or not. The PCR stores STC timeinformation corresponding to an ATS showing when the PCR packet istransferred to a decoder, in order to achieve synchronization between anArrival Time Clock (ATC) that is a time axis of ATSs, and an System TimeClock (STC) that is a time axis of PTSs and DTSs.

FIG. 25 illustrates the data structure of the PMT in detail. A PMTheader is disposed at the top of the PMT. The PMT header describes thelength of data included in the PMT and others. A plurality ofdescriptors relating to the multiplexed data is disposed after the PMTheader. Information such as the copy control information is described inthe descriptors. After the descriptors, a plurality of pieces of streaminformation relating to the streams included in the multiplexed data isdisposed. Each piece of stream information includes stream descriptorseach describing information, such as a stream type for identifying acompression codec of a stream, a stream PID, and stream attributeinformation (such as a frame rate or an aspect ratio). The streamdescriptors are equal in number to the number of streams in themultiplexed data.

When the multiplexed data is recorded on a recording medium and others,it is recorded together with multiplexed data information files.

Each of the multiplexed data information files is management informationof the multiplexed data as shown in FIG. 26. The multiplexed datainformation files are in one to one correspondence with the multiplexeddata, and each of the files includes multiplexed data information,stream attribute information, and an entry map.

As illustrated in FIG. 26, the multiplexed data information includes asystem rate, a reproduction start time, and a reproduction end time. Thesystem rate indicates the maximum transfer rate at which a system targetdecoder to be described later transfers the multiplexed data to a PIDfilter. The intervals of the ATSs included in the multiplexed data areset to not higher than a system rate. The reproduction start timeindicates a PTS in a video frame at the head of the multiplexed data. Aninterval of one frame is added to a PTS in a video frame at the end ofthe multiplexed data, and the PTS is set to the reproduction end time.

As shown in FIG. 27, a piece of attribute information is registered inthe stream attribute information, for each PID of each stream includedin the multiplexed data. Each piece of attribute information hasdifferent information depending on whether the corresponding stream is avideo stream, an audio stream, a presentation graphics stream, or aninteractive graphics stream. Each piece of video stream attributeinformation carries information including what kind of compression codecis used for compressing the video stream, and the resolution, aspectratio and frame rate of the pieces of picture data that is included inthe video stream. Each piece of audio stream attribute informationcarries information including what kind of compression codec is used forcompressing the audio stream, how many channels are included in theaudio stream, which language the audio stream supports, and how high thesampling frequency is. The video stream attribute information and theaudio stream attribute information are used for initialization of adecoder before the player plays back the information.

In the present embodiment, the multiplexed data to be used is of astream type included in the PMT. Furthermore, when the multiplexed datais recorded on a recording medium, the video stream attributeinformation included in the multiplexed data information is used. Morespecifically, the image coding method or the image coding apparatusdescribed in each of embodiments includes a step or a unit forallocating unique information indicating video data generated by theimage coding method or the image coding apparatus in each ofembodiments, to the stream type included in the PMT or the video streamattribute information. With the configuration, the video data generatedby the image coding method or the image coding apparatus described ineach of embodiments can be distinguished from video data that conformsto another standard.

Furthermore, FIG. 28 illustrates steps of the moving picture decodingmethod according to the present embodiment. In Step exS100, the streamtype included in the PMT or the video stream attribute informationincluded in the multiplexed data information is obtained from themultiplexed data. Next, in Step exS101, it is determined whether or notthe stream type or the video stream attribute information indicates thatthe multiplexed data is generated by the image coding method or theimage coding apparatus in each of embodiments. When it is determinedthat the stream type or the video stream attribute information indicatesthat the multiplexed data is generated by the image coding method or theimage coding apparatus in each of embodiments, in Step exS102, decodingis performed by the image decoding method in each of embodiments.Furthermore, when the stream type or the video stream attributeinformation indicates conformance to the conventional standards, such asMPEG-2, MPEG-4 AVC, and VC-1, in Step exS103, decoding is performed by amoving picture decoding method in conformity with the conventionalstandards.

As such, allocating a new unique value to the stream type or the videostream attribute information enables determination whether or not theimage decoding method or the image decoding apparatus that is describedin each of embodiments can perform decoding. Even when multiplexed datathat conforms to a different standard is input, an appropriate decodingmethod or apparatus can be selected. Thus, it becomes possible to decodeinformation without any error. Furthermore, the image coding method orapparatus, or the image decoding method or apparatus in the presentembodiment can be used in the devices and systems described above.

[Embodiment 4]

Each of the image coding method, the image coding apparatus, the imagedecoding method, and the image decoding apparatus in each of embodimentsis typically achieved in the form of an integrated circuit or a LargeScale Integrated (LSI) circuit. As an example of the LSI, FIG. 29illustrates a configuration of the LSI ex500 that is made into one chip.The LSI ex500 includes elements ex501, ex502, ex503, ex504, ex505,ex506, ex507, ex508, and ex509 to be described below, and the elementsare connected to each other through a bus ex510. The power supplycircuit unit ex505 is activated by supplying each of the elements withpower when the power supply circuit unit ex505 is turned on.

For example, when coding is performed, the LSI ex500 receives an AVsignal from a microphone ex117, a camera ex113, and others through an AV10 ex509 under control of a control unit ex501 including a CPU ex502, amemory controller ex503, a stream controller ex504, and a drivingfrequency control unit ex512. The received AV signal is temporarilystored in an external memory ex511, such as an SDRAM. Under control ofthe control unit ex501, the stored data is segmented into data portionsaccording to the processing amount and speed to be transmitted to asignal processing unit ex507. Then, the signal processing unit ex507codes an audio signal and/or a video signal. Here, the coding of thevideo signal is the coding described in each of embodiments.Furthermore, the signal processing unit ex507 sometimes multiplexes thecoded audio data and the coded video data, and a stream IO ex506provides the multiplexed data outside. The provided multiplexed data istransmitted to the base station ex107, or written on the recordingmedium ex215. When data sets are multiplexed, the data should betemporarily stored in the buffer ex508 so that the data sets aresynchronized with each other.

Although the memory ex511 is an element outside the LSI ex500, it may beincluded in the LSI ex500. The buffer ex508 is not limited to onebuffer, but may be composed of buffers. Furthermore, the LSI ex500 maybe made into one chip or a plurality of chips.

Furthermore, although the control unit ex501 includes the CPU ex502, thememory controller ex503, the stream controller ex504, the drivingfrequency control unit ex512, the configuration of the control unitex501 is not limited to such. For example, the signal processing unitex507 may further include a CPU. Inclusion of another CPU in the signalprocessing unit ex507 can improve the processing speed. Furthermore, asanother example, the CPU ex502 may serve as or be a part of the signalprocessing unit ex507, and, for example, may include an audio signalprocessing unit. In such a case, the control unit ex501 includes thesignal processing unit ex507 or the CPU ex502 including a part of thesignal processing unit ex507.

The name used here is LSI, but it may also be called IC, system LSI,super LSI, or ultra LSI depending on the degree of integration.

Moreover, ways to achieve integration are not limited to the LSI, and aspecial circuit or a general purpose processor and so forth can alsoachieve the integration. Field Programmable Gate Array (FPGA) that canbe programmed after manufacturing LSIs or a reconfigurable processorthat allows re-configuration of the connection or configuration of anLSI can be used for the same purpose.

In the future, with advancement in semiconductor technology, a brand-newtechnology may replace LSI. The functional blocks can be integratedusing such a technology. The possibility is that the present inventionis applied to biotechnology.

[Embodiment 5]

When video data generated in the image coding method or by the imagecoding apparatus described in each of embodiments is decoded, comparedto when video data that conforms to a conventional standard, such asMPEG-2, MPEG-4 AVC, and VC-1 is decoded, the processing amount probablyincreases. Thus, the LSI ex500 needs to be set to a driving frequencyhigher than that of the CPU ex502 to be used when video data inconformity with the conventional standard is decoded. However, when thedriving frequency is set higher, there is a problem that the powerconsumption increases.

In order to solve the problem, the moving picture decoding apparatus,such as the television ex300 and the LSI ex500 is configured todetermine to which standard the video data conforms, and switch betweenthe driving frequencies according to the determined standard. FIG. 30illustrates a configuration ex800 in the present embodiment. A drivingfrequency switching unit ex803 sets a driving frequency to a higherdriving frequency when video data is generated by the image codingmethod or the image coding apparatus described in each of embodiments.Then, the driving frequency switching unit ex803 instructs a decodingprocessing unit ex801 that executes the image decoding method describedin each of embodiments to decode the video data. When the video dataconforms to the conventional standard, the driving frequency switchingunit ex803 sets a driving frequency to a lower driving frequency thanthat of the video data generated by the image coding method or the imagecoding apparatus described in each of embodiments. Then, the drivingfrequency switching unit ex803 instructs the decoding processing unitex802 that conforms to the conventional standard to decode the videodata.

More specifically, the driving frequency switching unit ex803 includesthe CPU ex502 and the driving frequency control unit ex512 in FIG. 29.Here, each of the decoding processing unit ex801 that executes themoving picture decoding method described in each of embodiments and thedecoding processing unit ex802 that conforms to the conventionalstandard corresponds to the signal processing unit ex507 in FIG. 29. TheCPU ex502 determines to which standard the video data conforms. Then,the driving frequency control unit ex512 determines a driving frequencybased on a signal from the CPU ex502. Furthermore, the signal processingunit ex507 decodes the video data based on the signal from the CPUex502. For example, the identification information described inEmbodiment 3 is probably used for identifying the video data. Theidentification information is not limited to the one described inEmbodiment 3 but may be any information as long as the informationindicates to which standard the video data conforms. For example, whenwhich standard video data conforms to can be determined based on anexternal signal for determining that the video data is used for atelevision or a disk, etc., the determination may be made based on suchan external signal. Furthermore, the CPU ex502 selects a drivingfrequency based on, for example, a look-up table in which the standardsof the video data are associated with the driving frequencies as shownin FIG. 32. The driving frequency can be selected by storing the look-uptable in the buffer ex508 and in an internal memory of an LSI, and withreference to the look-up table by the CPU ex502.

FIG. 31 illustrates steps for executing a method in the presentembodiment. First, in Step exS200, the signal processing unit ex507obtains identification information from the multiplexed data. Next, inStep exS201, the CPU ex502 determines whether or not the video data isgenerated by the coding method and the coding apparatus described ineach of embodiments, based on the identification information. When thevideo data is generated by the moving picture coding method and themoving picture coding apparatus described in each of embodiments, inStep exS202, the CPU ex502 transmits a signal for setting the drivingfrequency to a higher driving frequency to the driving frequency controlunit ex512. Then, the driving frequency control unit ex512 sets thedriving frequency to the higher driving frequency. On the other hand,when the identification information indicates that the video dataconforms to the conventional standard, such as MPEG-2, MPEG-4 AVC, andVC-1, in Step exS203, the CPU ex502 transmits a signal for setting thedriving frequency to a lower driving frequency to the driving frequencycontrol unit ex512. Then, the driving frequency control unit ex512 setsthe driving frequency to the lower driving frequency than that in thecase where the video data is generated by the image coding method andthe image coding apparatus described in each of embodiment.

Furthermore, along with the switching of the driving frequencies, thepower conservation effect can be increased by changing the voltage to beapplied to the LSI ex500 or an apparatus including the LSI ex500. Forexample, when the driving frequency is set lower, the voltage to beapplied to the LSI ex500 or the apparatus including the LSI ex500 isprobably set to a voltage lower than that in the case where the drivingfrequency is set higher.

Furthermore, when the processing amount for decoding is larger, thedriving frequency may be set higher, and when the processing amount fordecoding is smaller, the driving frequency may be set lower as themethod for setting the driving frequency. Thus, the setting method isnot limited to the ones described above. For example, when theprocessing amount for decoding video data in conformity with MPEG-4 AVCis larger than the processing amount for decoding video data generatedby the moving picture coding method and the moving picture codingapparatus described in each of embodiments, the driving frequency isprobably set in reverse order to the setting described above.

Furthermore, the method for setting the driving frequency is not limitedto the method for setting the driving frequency lower. For example, whenthe identification information indicates that the video data isgenerated by the moving picture coding method and the moving picturecoding apparatus described in each of embodiments, the voltage to beapplied to the LSI ex500 or the apparatus including the LSI ex500 isprobably set higher. When the identification information indicates thatthe video data conforms to the conventional standard, such as MPEG-2,MPEG-4 AVC, and VC-1, the voltage to be applied to the LSI ex500 or theapparatus including the LSI ex500 is probably set lower. As anotherexample, when the identification information indicates that the videodata is generated by the moving picture coding method and the movingpicture coding apparatus described in each of embodiments, the drivingof the CPU ex502 does not probably have to be suspended. When theidentification information indicates that the video data conforms to theconventional standard, such as MPEG-2, MPEG-4 AVC, and VC-1, the drivingof the CPU ex502 is probably suspended at a given time because the CPUex502 has extra processing capacity. Even when the identificationinformation indicates that the video data is generated by the movingpicture coding method and the moving picture coding apparatus describedin each of embodiments, in the case where the CPU ex502 has extraprocessing capacity, the driving of the CPU ex502 is probably suspendedat a given time. In such a case, the suspending time is probably setshorter than that in the case where when the identification informationindicates that the video data conforms to the conventional standard,such as MPEG-2, MPEG-4 AVC, and VC-1.

Accordingly, the power conservation effect can be increased by switchingbetween the driving frequencies in accordance with the standard to whichthe video data conforms. Furthermore, when the LSI ex500 or theapparatus including the LSI ex500 is driven using a battery, the batterylife can be extended with the power conservation effect.

[Embodiment 6]

There are cases where a plurality of video data that conforms todifferent standards, is provided to the devices and systems, such as atelevision and a cellular phone. In order to enable decoding theplurality of video data that conforms to the different standards, thesignal processing unit ex507 of the LSI ex500 needs to conform to thedifferent standards. However, the problems of increase in the scale ofthe circuit of the LSI ex500 and increase in the cost arise with theindividual use of the signal processing units ex507 that conform to therespective standards.

In order to solve the problem, what is conceived is a configuration inwhich the decoding processing unit for implementing the moving picturedecoding method described in each of embodiments and the decodingprocessing unit that conforms to the conventional standard, such asMPEG-2, MPEG-4 AVC, and VC-1 are partly shared. Ex900 in FIG. 33A showsan example of the configuration. For example, the moving picturedecoding method described in each of embodiments and the moving picturedecoding method that conforms to MPEG-4 AVC have, partly in common, thedetails of processing, such as entropy coding, inverse quantization,deblocking filtering, and motion compensated prediction. The details ofprocessing to be shared probably include use of a decoding processingunit ex902 that conforms to MPEG-4 AVC. In contrast, a dedicateddecoding processing unit ex901 is probably used for other processingunique to an aspect of the present invention. The decoding processingunit for implementing the moving picture decoding method described ineach of embodiments may be shared for the processing to be shared, and adedicated decoding processing unit may be used for processing unique tothat of MPEG-4 AVC.

Furthermore, ex1000 in FIG. 33B shows another example in that processingis partly shared. This example uses a configuration including adedicated decoding processing unit ex1001 that supports the processingunique to an aspect of the present invention, a dedicated decodingprocessing unit ex1002 that supports the processing unique to anotherconventional standard, and a decoding processing unit ex1003 thatsupports processing to be shared between the image decoding methodaccording to the aspect of the present invention and the conventionalmoving picture decoding method. Here, the dedicated decoding processingunits ex1001 and ex1002 are not necessarily specialized for theprocessing according to the aspect of the present invention and theprocessing of the conventional standard, respectively, and may be theones capable of implementing general processing. Furthermore, theconfiguration of the present embodiment can be implemented by the LSIex500.

As such, reducing the scale of the circuit of an LSI and reducing thecost are possible by sharing the decoding processing unit for theprocessing to be shared between the image decoding method according tothe aspect of the present invention and the moving picture decodingmethod in conformity with the conventional standard.

[Industrial Applicability]

The image coding method and the image decoding method according to thepresent invention has an effect of improve coding efficiency, and can beapplied to a video camera, a mobile phone having the function ofcapturing and reproducing video, a personal computer, a recording andreproducing apparatus, or the like.

REFERENCE SIGNS LIST

1000 Image coding apparatus

1100 Coding processing unit

1101 Subtractor

1102 Orthogonal transform unit

1103 Quantization unit

1104 Entropy coding unit

1105 Inverse quantization unit

1106 Inverse orthogonal transform unit

1107 Adder

1108 Deblocking filter

1109 Memory

1110 Intra prediction unit

1111 Motion compensation unit

1112 Motion estimation unit

1113 Switch

1200 Coding processing unit

2000 Image decoding apparatus

2100 Decoding processing unit

2101 Entropy decoding unit

2102 Inverse quantization unit

2103 Inverse orthogonal transform unit

2104 Adder

2105 Deblocking filter

2106 Memory

2107 Intra prediction unit

2108 Motion compensation unit

2109 Switch

2200 Decoding control unit

The invention claimed is:
 1. An image coding method for generating acoded stream which includes a plurality of processing units and a headerof the processing units, by coding a moving picture using interprediction, the processing units including at least one processing unitdivided into a plurality of sub processing units in a hierarchy whichdecrease in size from a higher level to a lower level, the hierarchyincluding: a highest hierarchical layer in which a coding unit exists asa largest processing unit; and a lower hierarchical layer which isdeeper than the highest hierarchical layer and in which a predictionunit exists as a processing unit smaller than the coding unit, the imagecoding method comprising: coding the moving picture using interprediction; writing, into the header, hierarchy depth information whichis information for identifying a hierarchical layer having a predictionunit in which a reference index necessary for decoding is stored andindicates a hierarchical layer higher than a lowest hierarchical layerin which a smallest prediction unit exists; and writing, into aprediction unit located at a hierarchical layer indicated by thehierarchy depth information or located higher than the indicatedhierarchical layer, the reference index to be applied to the predictionunit.
 2. An image coding apparatus for generating a coded stream whichincludes a plurality of processing units and a header of the processingunits, by coding a moving picture using inter prediction, the processingunits n at least one processing unit divided into a plurality of subprocessing units in a hierarchy which decrease in size from a higherlevel to a lower level, the hierarchy including: a highest hierarchicallayer in which a coding unit exists as a largest processing unit; and alower hierarchical layer which is deeper than the highest hierarchicallayer and in which a prediction unit exists as a processing unit smallerthan the coding unit, the image coding apparatus comprising: anon-transitory, computer-readable memory device; and a hardwareprocessor that executes an image coding process including: coding themoving picture using inter prediction; writing, into the header,hierarchy depth information which is information for identifying ahierarchical layer having a prediction unit in which a reference indexnecessary for decoding is stored and indicates a hierarchical layerhigher than a lowest hierarchical layer in which a smallest predictionunit exists; and writing, into a prediction unit located at ahierarchical layer indicated by the hierarchy depth information orlocated higher than the indicated hierarchical layer, the referenceindex to be applied to the prediction unit.